Process for producing carbon black



Feb. 14, 1961 I. WILLIAMS PROCESS FOR PRODUCING CARBON BLACK Filed Aug.2, 1956 WAT R 14 F'UEL INVEN TO R Ira LULIILamA BY fulfil 9,.

Lflal M ATTORNEYS United States Patent Ofiice 2,971,822 Patented Feb.14, 1961 2,971,822 PROCESS FOR PRODUCING CARBON BLACK Ira Williams,Berger, Tex., assignor to J. M. Huber Corporation, Berger, Tex., acorporation of New Jersey Filed Aug. 2, 1956, Ser. No. 601,675 7 Claims.(Cl. 23-2094) This invention relates to an improved process for makingcarbon black by the controlled thermal decomposition of hydrocarbons andto an improved furnace in which the process can be carried out.

In my United States Patent No. 2,625,466, issued January 13, 1953, Ihave described a furnace for the production of carbon black composed ofa combustion chamber having an inlet wall, a substantially flat exit endwall and side walls enclosing a combustion chamber relatively fiat frominlet to outlet wall, a hydrocarbon injector tube in the center of theinlet end wall opening into the combustion chamber coaxially therewithand terminating in a nozzle producing a spray in the shape of a coneexpanding at an angle of from about 20-30, a series of burners openinginto the inlet end of the combustion chamber at a plurality of positionsaround the combustion chamber adjacent the side walls and mountedperpendicularly for discharging in the direction of the exit end wall,an outlet orifice in the center of the exit end wall of an area equal tothat of the base of the spray cone, and a reaction chamber in opencommunication with the combustion chamber through said outlet orifice.

In this prior furnace, carbon black is produced by a method involvinginjecting into the combustion chamber, at the plurality of positionsaround the combustion chamber adjacent the side walls, a combustiblemixture of a hydrocarbon fuel and air, directing the mixture and thecombustion gases formed fi'om the burning mixture perpendicularly to theexit end wall such that they impinge on said wall in such manner as tocause the combustion gases to become violently turbulent land to fiow tothe center of the combustion chamber, thence to the outlet orifice,simultaneously injecting into the combustion chamber from the inlet orhead end thereof an expanding cone of a substantially gaseoushydrocarbon, directing such cone of hydrocarbon axially of thecombustion chamber into the turbulent mass of combustion gases towardand in large pant through the outlet orifice into the reaction chamberwhere the carbon for the most part is formed.

Whereas this prior process and apparatus successfully produce carbonblack, it is difficult to control the operations in such manner thatcarbon of uniform quality is invariably obtained. Accordingly, a primaryobject of the present invention is to provide a process and apparatushaving all the advantages of the earlier invention but which is easilycontrolled to provide carbon of constant uniform quality. Another objectis to produce carbon of fine particle size leading to superiorperformance in various commercial products using the same.

In relation to the furnace of said prior patent, the apparatus of thepresent invention includes a combustion chamber which is likewiserelatively fiat from inlet to outlet wall, having similar arrangementsof the burners and hydrocarbon injector tube and an outlet orifice inthe center of the exit wall. The new furnace differs in several primaryrespects including the conversion of the combustion chamber into acombination combustion-reaction chamber, the carbon being produced forthe most part or substantially wholly in this chamber, leaving at mostonly a small amount to be completed in the reaction chamber openlycommunicating with the outlet orifice, this said latter mentionedchamber now serving primarily as a quenching chamber.

These major diiferences include the following:

(1) A different spray nozzle, employed as the hydrocarbon injector tubeextending through the inlet wall, is of a character which introduces thehydrocarbon in the shape of a substantially hollow wide angle cone sprayor mist of very fine particle size.

(2) The central outlet orifice in the opposite end wall is ofsufiiciently small area in relation to said wall and to said cone ofsprayed material that not only are the flame and combustion gases causedto impinge upon the exit wall for effecting violent turbulence in thechamber, but the sprayed hydrocarbon is caused to flow obliquely towardthe side wall or walls of the chamber and into the turbulent mass ratherthan in the direction of the outlet orifice.

(3) The chamber connected to said outlet orifice, here serves almostentirely for cooling the reaction mass and is provided with a fluidspray arranged for rapidly accomplishing the quenching function. V

For obtaining carbon of better or optimum quality or under moredesirable or optimum conditions, the dimensions of the various parts ofthe furnace of the invention differ from those of the prior furnace, allas hereinafter disclosed.

In the drawing:

Fig. l is a vertical section through the center of the furnace, and

Fig. 2 is a horizontal section taken on line 2-2 of 'Fig. 1.

With reference to the drawing, there is illustrated acombustion-reaction chamber 12 of relatively shallow depth from the topor inlet end to the bottom or outlet end, this chamber preferably beingof cylindrical shape having a depth from about /2 to about equal thediameter. The head or inlet end 13 is provided with a multiplicity ofburners 14, suitably eight, substantially at the extremities of theinlet end and mounted such that the flame produced travels along andadjacent to the side walls in a direction perpendicular to the exitwall. The inlet wall 13 is provided with an opening 15 directed axiallyof the reaction chamber.

The outlet or bottom end wall of the chamber contains a centrallylocated outlet onfi-ce 16 which should be of from about 3 to 10% of thearea of the end wall. This outlet orifice is in open communication withthe cooling or quenching chamber 17 in turn discharging through theoutlet tube 18 leading to a carbon collecting means (not shown). Theheat-resistant, refractory Walls of the furnace are covered with a steeljacket 19 which extends beyond the combustion reaction chamber 12 andforms a plenum chamber 26 into which air is introduced through the inletconduit 21 from a fan (not shown). The plenum chamber 20 is designed tosupply air at any pressure up to about inches of water.

The burners 14 are supplied with hydrocarbon fuel by means of pipe 22.The hydrocarbon feed stock to be decomposed into carbon is introducedthrough conduit 23 extending through the opening 15 and terminating inthe nozzle 27 of the character hereinafter described. The

wall of the furnace adjacent the quenching chamber 17 is provided withone or more openings 24 near or adjacent the outlet orifice 16 throughwhich pipes extend, terminating in spray heads 25, adapted to spraycooling fluid.

The volume of the cooling chamber 17 is suitably from to 50% of thevolume of the combustion-reaction chamber and its shape, preferablycylindrical, is such that it permits rapid quenching of the carbon ladengases. A suitable size for the quenching chamber 17 is one having across-sectional area of about twice that of the outlet orificecommunicating therewith from the combustion- .reaction chamber. Toobtain adequately quick cooling in this chamber, the first or topcooling spray nozzle 25 should be mounted only a short distance from theoutlet orifice 16 and with this arrangement the initial quenching of thecarbon laden gases is efiected in about .005 to .01 second after leavingthe combustion-reaction chamber.

In View of the higher velocity of chemical reaction involved in theprocess of the invention, the carbon-producing hydrocarbon is preferablyone of considerable positive free energy. Normally liquid or oilyhydrocarbons of substantial molecular weight can be used, thosepreferred being highly unsaturated or aromatic hydrocarbons. Saturatedhydrocarbons of 9 or more carbon atoms can be successfully employed andthose of a lesser number of carbon atoms are of relatively little value.

The amount of air introduced into the combustion chamber may be variedto a substantial extent and suitably can be from somewhat more air thanthat required for complete combustion of the fuel to an amount as highas half the theoretical quantity necessary to burn both the fuel and thecarbon-producing hydrocarbon. The amount of air or oxygen employed mayprovide a considerable excess of free oxygen in the cooled gases, forthe reaction is ordinarily accomplished so rapidly that completecombustion of the oxygen need not take place.

The combustion and carbon-producing are most effectively accomplishedunder one embodiment of the invention when the intake and dischargingrates of the furnace are controlled in such manner as to provide apositive pressure in the combustion-reaction chamber, the preferredconditions being a pressure of at least inches of water.

To accomplish required subdivision and directional flow of thehydrocarbon feed, the spray nozzle 27 in the injector tube may beprovided with a perforated disk, and the thickness of the disk willprovide the hollow cone spray and determine the angle of the cone, thewidest angle being produced by a thin disk and the narrowest angle by athicker disk. A conventional spray nozzle of a type providing a whirlingmass of hydrocarbon just before it enters the opening in the flat diskcan be successfully employed. In accomplishing the spraying operation,the disk should be such as to provide a cone-shaped spray of a minimumangle of about 50, it being necessary, as stated, that the spray cone besubstantially hollow. Cone sprays of angles up to 140 give carbons ofincreasingly fine particle size. Spray angles of substantially less than50", such as one of 40 or less, yield carbon of more than twice theparticle sizes obtained with the use of angles between about 56 and 159.

The location and positioning of the burners to provide a ring of flameand combustion gases adjacent to the side walls of the reaction chamberare of importance to the success of the furnace in causing the flame toimpinge on the exit wall or ledge 26 of the combustion reaction chamberwhereby the flame cannot be blown away from the burner when the furnaceis operated at high velocities and a turbulent mass of hot gases isprovided in the chamber.

The construction of the furnace as described above brings about anextremely rapid intermingling of the carbon-producing hydrocarbon withthe hot combustion gases whereby most perfect and rapid vaporization ofthe hydrocarbon in mist form occurs and a higher dilution of thehydrocarbon with hot inert gases is obtained. The highly desirableultimate result is that carbon particles of much finer grade can be andare obtained.

, For producing the highly desirable or optimum results the conditionsof operation must be carefully controlled.

In general the reaction must be carried out in a very short period oftime. The space velocity through the furnace should be from 300 to 790cu. feet per cu. foot per minute based on the volume of the gas measuredunder normal atmospheric conditions, and the gases should become heatedin the range of 2200 to 2750 C. Under these conditions the residencetime of the reactants in the reaction chamber is of the order of .013 to.03 second. The carbon-producing hydrocarbon is decomposed almostcompletely within the combustion reaction chamber and the carbonparticles formed are of a smallness previously unattainable.

Example 1 A vertical furnace such as shown in the drawing was used. Ithad a shallow combustion-reaction chamber 15 nected to this orifice was12 inches in diameter and 40 inches long. The water spray in thequenching chamber was connected in at a level 18 inches below the exitor bottom surface of the combustion-reaction chamber.

For accomplishing the heating, the fuel used was natural gas of 1020B.t.u. rating. This gas together with air was burned in eight inspiratortype burners extending through the head of the combustion-reactionchamber. The hydrocarbon to be cracked was a viscous residue from thecatalytic cracking of petroleum having an A.P.I. gravity of 2.6, adistillation range between 370 and 680 F. and an aniline number of 53.This oil was preheated to 625 F. and then forced at a pressure of about150 pounds per square inch at a rate of 2.9 gallons per minute throughthe injector tube in the center of the inlet head of the furnace intoand through one of several nozzles producing sprayed hydrocarbon in theform of a hollow cone of differing angles as indicated below, the spraynozzles projecting below the inner surface of the head about /2 inch.

One hundred ninety-seven cubic feet of gas and 2929 cubic feet of airper minute were supplied to the burners. One hundred twenty cubic feetof air per minute were introduced through the head around thehydrocarbon injector tube which was cooled by the air. All gases weremeasured at 30 inches of mercury pressure at a temperature of 60 F.These rates of gas and air introduction provided a space velocity of 570cubic feet per cubic foot per minute for gas passage through thefurnace. The temperature within the combustion-reaction chamber wasapproximately 2550 to 2750 F.

In carrying out the processes of the several tests disks of difierentthicknesses were employed to provide cones of the varied degrees ofspread set forth in the following table. Samples of the carbons producedin the respective tests were collected and examined for particle sizeand tested for tinting strength in a newspaper ink composition. Theresults determined were as follows:

Tinting Degrees Lbs. Ave. Dia. Strength, Test spread of Yield in Milli-Percent of Cone per Gal. microns Channel Carbon The carbons produced bytests 1 and 5 were also compared by testing them for reinforcing actionin smoked sheet rubber compounds. It was found that 35 parts of theproduct of test 5 produced the degree of stillness obtained only by theuse of 50 parts of the product of test 1.

In another series of tests carried out in substantially The same furnacedescribed in the above example was employed except that the gas burnersthere used were replaced with atomizing oil burners. The hydrocarbonfuel employed as well as the carbon-producing hydrocarbon used in thisprocess had an A.P.I. gravity of 18 and an aromatic content of 47%. Thisoil was preheated to 450 F. before being introduced into the furnace,both that used for burning and that used for cracking. Air wasintroduced at the rate of 3030 cubic feet of air per minute and the oilwas burned at the rate of one gallon per minute. Thirty cubic feet ofair per minute were introduced around the hydrocarbon injector tube. Theoil was introduced through the injector tube at the rate of 3 gallonsper minute in the form of a hollow cone spray of a 140 angle. Thetemperature within the reaction chamber was approximately 2680 F.

The carbon was collected by passing the same through an electricalprecipitator and cyclone collectors, and it had a bulk density of onlyabout 0.3 pound per cubic foot, the diameter of the particles beingabout 6 miliimicrons.

Example 3 A furnace similar to that used in Example 1 was employed.However, the outlet orifice from the combustion reaction chamber wasonly 5.6 inches in diameter and the quenching chamber was only 9 inchesin diameter. Natural gas having a B.t.u. value of 1050 per cubic footwas introduced into the eight burners at a rate of 169 cubic feet perminute. Air was introduced through the burners at the rate of 2215 cubicfeet per minute and into the opening surrounding the hydrocarboninjector tube at the rate of 98.5 cubic feet per minute. The crackingstock employed was a catalytic recycle oil obtained as a by-product fromthe manufacture of gasoline, having a distillation range of 370-597 F.,and 52% of the content was soluble in sulfuric acid. After beingpreheated to 600 F. the oil was injected through the hydrocarboninjector tube into the furnace at the rate of 3.5 gallons per minute inthe form of a substantially hollow cone having a spray head or angle of140. The temperature within the reaction chamber was approximately 2710F.

The carbon-laden reaction gases were quenched to a temperature of 1200"F. by means of water sprayed downwardly in the quenching chamber at apoint 30 inches from the outlet surface of the combustion-reactionchamber. In the lower part of the quenching chamber the gases werefurther quenched to a temperature of 425 F. after which the gases werepassed through an electrical precipitator and cyclone collecting system.The collected carbon had a bulk density of about 0.3 pound per cubicfoot, and the average diameter of the particles was about 6millimicrons.

' The carbon produced by the process of this example was compared with astandard I.S.A.F. carbon (produced in an intermediate super abrasionfurnace) by compounding the respective carbons in rubber compositions ofcomparable constitution, the formulas being appropriately changed tocompensate for the differences in the surface areas of the carbon andthe amount used of the carbon produced by the present invention beingonly 70% of that employed in the formula containing the I.S.A.F. carbon.

GRS Synthetic rubber 100 I.S.A.F. carbon 50 Experimental carbon. 35 Zinc0xide. 5 Ste-trio aci 1. 5 1.5 S ur- 1. 8 2.0 Mineral O 7. 5 7. 6Santccure 1.0 1. 2

1 Santocure is a reaction product of mcrcaptobcnzothiazolc andcyclohexylarnine.

Each of these compounds was vulcanized at 300 F. for 60 minutes.

It should be understood that the present invention is not limited to thedetails of apparatus and operating conditions herein described but thatit extends to all equivalents which will occur to those skilled in theart upon consideration of the terms and scope of the claims appendedhereto.

I claim:

1. In a carbon-producing process employing a combustion chamber ofshallow depth from end to end having in one end wall a centrally locatedhydrocarbon injector and burner means disposed around said chamber, saidburner means being supplied with fuel and excess air and projectingflames and gases directly along the side wall of said chamber intoimpingement with its other end wall to maintain a turbulent mass offlames and gases around said chamber adjacent said other end wall, saidother end wall having an outlet orifice substantially at its center, thesteps which comprise introducing into said chamber through said injectora mist of a carbon-producing hydrocarbon oil of positive free energy inthe form of a hollow cone expanding obliquely toward said side wall intosaid turbulent mass of flames and gases, the angle of said cone being atleast 50, decomposing said hydrocarbon oil predominantly within saidchamber, flowing the resulting carbon and reaction gases through saidoutlet orifice, and quenching the outflow promptly after its emergencefrom said outlet orifice, whereby carbon of extremely fine particle sizeis obtained.

2. In a carbon-producing process employing a combustion chamber ofshallow depth from end to end having in one end wall a centrally locatedhydrocarbon injector and burner means disposed around said chamber, saidburner means being supplied with fuel and excess air and projectingflames and gases directly along the side wall of said chamber'intoimpingement with its other end wall to maintain a turbulent mass offlames and gases around said chamber adjacent said other end wall, saidother end wall having an outlet orifice substantially at its center, thesteps which comprise introducing into said chamber through said injectora mist of a carbon-producing hydrocarbon oil of positive free energy inthe form of a hollow cone expanding obliquely toward said side wall intosaid turbulent mass of flames and gases, the angle of said cone beingbetween 50 and decomposing said hydrocarbon oil predominantly withinsaid chamber, flowing the resulting carbon and reaction gases throughsaid outlet orifice, and quenching the outflow promptly after itsemergence from said outlet orifice, whereby carbon of extremely fineparticle size is obtained.

3. In a carbon-producing process employing a combustion chamber of.shallow depth from end to end having in one end wall a centrally locatedhydrocarbon injector and burner means disposed around said chamber, saidburner means being supplied with fuel and excess air and projectingflames and directly along the side wall of said chamber into impingementwith its other end wall to maintain a turbulent mass of flames and gasesaround said chamber adjacent said other end wall, said other end wallhaving an outlet orifice substantially at 'its center, theisteps'whichcomprise introducing into said chamber through said injector a mist of acarbon-producing hydrocarbon oil of positive free energy, in the form ofa hollow cone expanding obliquely toward said side wall into saidturbulent mass of flames and gases, the angle of said cone being atleast 50, decomposing said hydrocarbon oil predominantly within saidchamber within a period of from .013 to .c3 second, flowing theresulting carbon and reaction gases through said outlet orifice, andquenching the outflow promptly after its emergence from said outletorifice, whereby carbon of extremely fine particle size is obtained.

4. In a carbon-producing process employing a combustion chamber ofshallow depth from end to end having in one end Wall a centrally locatedhydrocarbon injector and burner means disposed around said chamber, saidburner means being supplied with fuel and excess air and projectingflames and gases directly along the side wall of said chamber intoimpingement with its other end wall to maintain a turbulent mass offlames and gases around said chamber adjacent said other end wall, saidother end Wall having an outlet orifice substantially at its center, thesteps which comprise introducing into said chamber through said injectora mist of a carbon-producing hydrocarbon oil of positive free energy inthe form of a hollow cone expanding obliquely toward said side wall intosaid turbulent mass of flames and gases, the angle of said cone being atleast 50 decomposing said hydrocarbon oil predominantly within saidchamber, flowing the resulting carbon and reaction gases through saidoutlet orifice, said oil, fuel and air being introduced at rates whichmaintain the outflow from said chamber at a space velocity of 300 to 700cubic feet per cubic foot per minute, and quenching the outflow promptlyafter its emergence from said outlet orifice, whereby carbon ofextremely fine particle size is obtained.

5. In a carbonproducing process employing a combustion chamber ofshallow depth from end to end having in one end wall a centrally locatedhydrocarbon injector and burner means disposed around said chamber, saidburner means being supplied with fuel and excess air and projectingflames and gases directly along the side wall of said chamber intoimpingement with its other end Wall to maintain a turbulent mass offlames and gases around said chamber adjacent said other end wall, saidother end Wall having an outlet orifice substantially at its center, thesteps which comprise introducing into said chamber through said injectora mist of a carbonproducing hydrocarbon oil of positive free energy inthe form of a hollow cone expanding obliquely toward said side wall intosaid turbulent mass of flames and gases, the angle of said cone being atleast 50 decomposing said hydrocarbon oil predominantly within saidchamber within a period of from .013 to .03 second, flowing theresulting carbon and reaction gases through said outlet orifice, andquenching the outflow within a period of from .005 to .01 second afterits emergence from said outlet orifice, whereby carbon of extremely fineparticle size is obtained. 7

6. In a carbon-producing process employing a combustion chamber ofshallow depth from end to end having in one end wall a centrally locatedhydrocarbon injector and burner means disposed around said chamber, saidburner means being supplied with fuel and excess air and projectingflames and gases directly along the side wall of said chamber intoimpingement with its other end wall to maintain a turbulent mass offlames and gases around said chamber adjacent said other end wall, saidother end wall having an outlet orifice substantially at its center, thesteps which comprise introducing into said chamber through said injectora mist of a carbon-producing hydrocarbon oil of positive free energy inthe form of a hollow cone expanding obliquely toward said side wall intosaid turbulent mass of flames and gases, the angle of said cone beingbetween 50 and decomposing said hydrocarbon oil predominantly withinsaid chamber, so proportioning said air to said fuel and said oil thatsubstantially all of said fuel and up to one-half of said oil isconsumed, flowing the re sulting carbon and reaction gases through saidoutlet orifice, and quenching the outflow promptly after its emergencefrom said outlet orifice, whereby carbon of extremely fine particle sizeis obtained.

7. In a carbon-producing process employing a combustion chamber ofshallow depth from end to end having in one end wall a centrally locatedhydrocarbon injector and burner means disposed around said chamber, saidburner means being supplied with fuel and excess air and projectingflames and gases directly along the side wall of said chamber intoimpingement with its other end wall to maintain a turbulent mass offlames and gases around said chamber adjacent said other end Wall, saidother end wall having an outlet orifice substantially at its center, thesteps which comprise introducing into said chamber through said injectora mist or" a carbon-producing hydrocarbon oil of positive free energy inthe form of a hollow cone expanding obliquely toward said side wall intosaid turbulent mass of fiames and gases, the angle of said cone beingbetween 50 and 150, decomposing said hydrocarbon oil predominantlywithin said chamber within a period of from .013 to ,03 econd, flowingthe resulting carbon and reaction gases through said outlet orifice,said oil, fuel and'air being introduced at rates which maintain theoutflow from said chamber at a space velocity of 300 to 700 cubic feetper cubic foot per minute and which maintain a positive pressureequivalent to at least 20 inches of water in said chamber, and quenchingthe outflow within a period of from .005 to .01 second after itsemergence from said outlet orifice, whereby carbon of extremely fineparticle size is obtained.

References Cited in the file of this patent UNITED STATES PATENTS2,625,466 Williams Jan. 13, 1953 FOREIGN PATENTS 733,735 Great BritainJuly 20, 1955 743,879 Great Britain Jan. 25, 1956 Ml Mini

1. IN A CARBON-PRODUCING PROCESS EMPLOYING A COMBUSTION CHAMBER OF SHALLOW DEPTH FROM END TO END HAVING IN ONE END WALL A CENTRALLY LOCATED HYDROCARBON INJECTOR AND BURNER MEAN DISPOSED AROUND SAID CHAMBER, SAID BURNER MEANS BEING SUPPLIED WITH FUEL AND EXCESS AIR AND PROJECTING FLAMES AND GASES DIRECTLY ALONG THE SIDE WALL OF SAID CHAMBER INTO IMPINGEMENT WITH ITS OTHER END WALL TO MAINTAIN A TURBULENT MASS OF FLAMES AND GASES AROUND SAID CHAMBER ADJACENT SAID OTHER END WALL, SAID OTHER END WALL HAVING AN OUTLET ORIFICE SUBSTANTIALLY AT ITS CENTER, THE STEPS WHICH COMPRISE INTRODUCING INTO SAID CHAMBER THROUGH SAID INJECTOR A MIST OF A CARBON-PRODUCING HYDROCARBON OIL OF POSITIVE FREE ENERGY IN THE FORM OF A HOLLOW CONE EXPANDING OBLIQUELY TOWARD SAID SIDE WALL INTO SAID TURBULENT MASS OF FLAMES AND GASES, THE 